Method utilizing a disposable blade in microtome cutting

ABSTRACT

The method of microtome cutting based on using the conventional, non-disposable, thick, inflexible microtome knife that requires resharpening after each period of wear and substantial blade holder adjustments to obtain and maintain the proper cutting angle is replaced by a method based on using a thin, flexible and disposable blade having a microtome quality cutting edge and which method allows the technician to install and replace blades without disturbing or repositioning the holder.

United States Patent Pickett [54] METHOD UTILIZING A DISPOSABLE BLADE IN MICROTOME CU'I'IING [72] Inventor: John E. P. Pickett, 3323 Pinafore Drive, Durham, NC. 27705 [22] Filed: March 22, 1971 [21] Appl. No.: 126,674

Related U.S. Application Data [63] Continuation-impart of Ser. No. 885,143, Dec.

15, 1969, Pat. No. 3,599,523.

[52] U.S. Cl.' ..83/13, 83/431, 83/9l5.5, I 83/651 [51] Int. Cl. ..B26d 3/00 [58] Field ofSearch ..83/13,915.5,43l,437,651,

[5 6] References Cited UNITED STATES PATENTS 1,865,539 7/1932 Pietzsch ..83/9l5.5 X

[4:] Oct.24, 1972 2,155,523 4/1939 Bausch et al. ..83/9l5.5 2,232,008 2/1941 MacDonald ..83/915.5 UX 2,439,671 4/1948 Ott ..83/915.5 3,190,164 6/1965 McCormick ..83/9l5.5 X 3,227,020 1/1966 Zeytoonian ..83/9 1 5.5

Primary Examiner-Andrew R. J uhasz Assistant ExaminerLeon Gilden Attorney-B. B. Olive [57] ABSTRACT The method of microtome cutting based on using the conventional, non-disposable, thick,- inflexible microtome knife that requires resharpening after each period of wear and substantial blade holder adjustments to obtain and maintain the proper cutting angle is replaced by a method based on using a thin, flexible and disposable blade having a microtome quality cutting edge and which method allows the technician to install and replace blades without disturbing or repositioning the holder.

9 Claims, 16 Drawing Figures rzplacerncnt blade PATENTEDnm 24 m2 sum 1 or 2 eplacemrznt blade INVENTOR. John E. P. Pickett ATTORNEY PATENTEDUBTZMQT? I 3.699.830

SHEET 2 [1F 2 1?. T1 If? I7 i I W H549 @mpe 2 6 W 62 FIG. 3 I 63 II I I INVENTOR. John E. P. Pickett I I hh BY I l h. r 1 1 I ATTORNEY METHOD UTILIZING A DISPOSABLE BLADE IN MICROTONIE CUTTING CROSS REFERENCE TO RELATED APPLICATION This application partakes of being a continuation-inpart of pending application Ser. No. 885,143 filed Dec. 15, 1969 entitled Disposable Blade and Holder for Microtome by the same inventor now US. Pat. No. 3,599,523.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to methods of microtome cutting using microtome knives or blades and knife or blade holders and particularly to methods of microtome cutting using disposable blade and disposable blade holder constructions.

2. Description of the Prior Art It has long been the practice in the art for microtome cutting procedures to be based on use of knives which take the form of being relatively thick, inflexible, and are adapted to being resharpened. Such knives are made of a very fine grade of steel and are adapted to receive an extremely sharp and relatively smooth cutting edge when sharpened. Such knives as seen in profile are biconcave, plane-concave, wedge shaped or tool edge shape sharpened. However, the conventional knives are expensive in initial cost, require expensive and time consuming resharpening equipment, require extra technician time for resharpening, require auxiliary hone plates and hone plate grinders, and the blades are susceptible to corrosion. The complexity and cost of resharpening microtome blades is further illustrated in my separate US. Pat. No. 3,349,520 which is for a machine designed to eliminate hand honing of the glass plates required to hone the blades. When such a blade is replaced or shifted laterally to get a fresh edge the blade holder may have to be readjusted, in either one or all directions, laterally, in tilt, forward and vertically. Therefore, the method of using conventional knives requires the availability of blade holders that can be adjusted in many directions. Such readjustments are absolutely necessary where precise and thin sectioning is involved since one conventional blade edge does not cut in the same precise manner as another conventional blade edge.

To illustrate how long established the practice has been, reference is made to US. Pat. No. 1,026,280 issued May l4, 1912 and which shows one method of cutting based on a type microtome knife that is in widespread use today. Over the years there have been many attempts to provide a method of cutting based on using a microtome blade holder adapted to receive some type of thin, highly flexible disposable blade such as a wafer type, double edge blades or typical single edge safety razor blades and representative prior patents are found in U. S. Pat. Nos. 1,865,539, 1,998,428, 2,232,008 and 3,227,020. Some of the prior patent microtome cutting methods using blade holders and disposable blades have found limited application in teaching laboratories where the cutting requirements are not critical and where relatively soft tissue is being cut. However, there has never appeared a practical method of using a disposable blade which provides quick change in the blade holder and adapts to use of a disposable blade having a microtome knife quality cutting edge capable of cutting not only the soft teaching tissue specimens but also a vwide range of bone, dense, hard tissue and the like in relatively wide widths of specimens. Furthermore, essentially all of the prior art methods of cutting that have reached the trade have been adapted to use the conventional very thin, wafer type blade or the single edge safety razor type which inherently exhibit a relatively rough cutting edge as compared to a microtome knife quality cutting edge. In addition to the conventional thin, disposable, wafer type double edge and single edge safety razor blades sold under such trademarks as Gillette, Wilkinson, Star, Personna and Gem another type of disposable blade used in surgical practice is the single edge, disposable blade sold under various trademarks, e.g., Personna and Weck. Blades of this type are widely used for surgical preparation, autopsies and general tissue cutting. The surgical Personna or Weck type blade like the Gem and Star single edge blade is normally provided on the unsharpened edge with a bent metal cover or banding member which gives rigidity to the blade and allows the user to safely hold the'blade for cutting. The surgical blade differs from the conventional double edge, wafer blade in that it is generally thicker, longer, and more elongated and rectangular in shape than most conventional single edge and double edge disposable wafer blades. The surgical blade is normally not flexed in use. However, when the mentioned cover member is removed from the surgical blade it has been found that while not as flexible as the usual wafer blade the surgical blades can nevertheless be flexed or slightly curved with a properly applied force. Of particular importance, the surgical blade, unlike the wafer blade, inherently lends itself to being made with an extremely sharp and relatively smooth edge of microtome knife quality whereas ordinary conventional single and double edge disposable blades even though suited to ordinary shaving do not in fact have either relatively smooth or sharp edges. While both conventional, disposable, single edge and double edge wafer type blades have been used in microtome blade holders for disposable blades, the art has not heretofore taught a cutting method built around the employment of the surgical type blade, e.g., those made by Personna or Weck, modified by removal of the mentioned cover member. Accordingly, the art of cutting has not had available av method utilizing a disposable blade having a cutting edge of microtome knife quality.

Another aspect of the method of cutting with both the conventional microtome knife as well as with such types of disposable blades as have been shown in prior art is that a change of blade almost always requires repositioning of the knife or blade holder before cutting is recommenced. If a blade or knife is nicked or damaged at the time of locating say a very thin and malignant tumor or lesion then if the blade is moved laterally for a sharp section or for replacement the chances are high that the tumor or lesion will be missed. This is so since the knife or blade after being unclamped and being shifted laterally or replaced may cause up to five succeeding sections to be missed in the course of getting the cutting thickness readjusted. Of equal significance is that many times when very thin sections, e.g., l to 2 microns, are being cut, the operator may have to try a number of supposedly sharp knives to find an acceptable cutting edge. The problem of knife damage and required resharpening, if not complete discard of the damaged knife, also arises whenever a hard cotton or nylon suture, surgical clip, gun pellet, calcium deposit or like foreign matter is embedded in the tissue being cut and strikes the knife edge.

Using the teaching of US. Pat. No. 1,865,539 as an example, it will be observed in another aspect of the prior art that prior art disposable wafer blade methods require loading of new wafers from the front of the holder. Since thefront of the holder is in the immediate cutting area where the tissue ribbons collect, each disposable blade change inherently requires disturbing this critical operational area and introduces the possibility of foreign matter, e.g., parafi'm, getting into the blade holder interior. The typical non-disposable knife has a front surface which acts as a guide for the ribbons of tissue. Therefore, this guide is removed each time the blade is replaced. For mass'sectioning it is the practice to collect the tissue in ribbons and mount the ribbons on a clear film strip base but prior art cutting methods do not adapt to such ribbon cutting. The film technique is increasing in importance and is explained in the article Improved Film Strip Technique for the Laboratory, Archives of Pathology, April 1964, Vol. 77, pages'429-433. It can be seen that conventional disposable blade techniques are not compatible with the new film techniques. Front loading blade change operations are furthermore generally awkward and slow and do not adapt to the requirements for holding blades being used to cut frozen tissue, e.g., a Cryostat microtome. A microtome blade method for using a disposable blade having a cutting edge of microtome knife quality, which adapts to film mounting procedures, which can cut any type tissue, bone, etc., cutby a microtome knife, which provides for side loading replacement and which adapts to both frozen and unfrozen tissue cutting has therefore not been provided by the prior art. This is particularly made evident by the fact that nov such disposable blade-holder method is in widespread use.

The typical prior art method can thus be said to generally involve all or substantially all of the following steps irrespective of whether the typical non-disposable thick microtome blade or disposable wafer type blade is employed: select blade, install blade, roughly adjust blade position laterally, in tilt, vertically and forwardly, take trial cuts, repeat adjustments of blade position to obtain an optimum position, trim sections until blade edge is dulled, replace blade, take trial cuts, readjust blade holder and repeat when blade is next dulled. In the case of the non-disposable blade there is of course involved the many additional and very expensive steps required to resharpen the blade after each use. In any event the prior art has not provided a method of cutting based on using a disposable blade and relative few operational steps for installing, using and replacing blades.

SUMMARY OF THE INVENTION According to the invention there is provided a method of cutting based on use of a precision machined microtome blade holder adapted to releasably receive the surgical type, single edge, disposable blade having a microtome knife quality edge for use in cutting all of the various type of thick, thin, soft, hard and dense tissue and bone specimens encountered in medical laboratory practice. The method of the invention enables a blade holder to be used which is adapted to be received by and clamped in the conventional precision microtome, adjustable knife clamp, so that no modification of the conventional microtome or clamp is required. According to the method of the invention, the surgical type blade is installed from the side, is clamped in cutting position and is slightly curved against a concave backing surface so that such blade curvature adds to the normal and optimum angle tilt of the blade holder, corresponding to the usual microtome knife tilt. This facilitates a proper angle of cut, optimum blade edge angle and clearance of the tissue block when moving past the blade. The blade is preferably chosen so that its length extends slightly beyond the maximum width of tissue block used on the rotary microtome which insures getting a full width of tissue cut with the widest block. For blade replacement the blade curving or clamping member having a convex clamping surface is moved from a blade clamping to a blade release position and in the release position a slot is formed in which a replacement blade is slid in from either side of the holder. The new blade is used to eject the worn blade being replaced without disturbing the blade holder which remains clamped in position. Furthermore, since the method of the invention provides for tissue ribbons to be guided on the clamping member front surface such ribbons are not disturbed during blade changes unlike the conventional disposable or nondisposable blade change. The amount of pressure applied to the blade is regulated as-required to regulate the blade curvature, which is preferably on about a 1 $41 inch radius.

The method of the invention adapts to cutting thick, thin, dense and both soft and hard specimens. The operator is assured that any replacement blade will do the job thus eliminating the requirement to check many knives and to search for a suitably sharpened knife when cutting very thin sections. When blades are 7 replaced the operator can immediately resume sectioning without fear of losing some critical and thin section in the course of restarting the cutting schedule. A fixed angle of cutting is immediately established as soon as the blade is installed and clamped and this angle will normally not change so long as the same type tissue is being cut. Yet, such angle can be quickly changed by adjusting the conventional microtome knife clamp. It should be noted that in comparison each change of a conventional knife normally requires angle adjustment of the blade holder since sharpening wears away at the knife edge. Also, if the conventional microtome knife is moved laterally to get a sharp cutting section the holder is often required to be adjusted in some direction.

From the viewpoint of costs it can be readily seen that conventional knife blade cutting, resharpening and replacement in terms of prior art methods is measured in terms of dollars per knife edge use whereas the disposable blade method of the invention involves cost per blade use measured in terms of cents.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial view of .a conventional microtome and knife clamp with a disposable blade holder adapted to the method of this invention shown mounted in the clamp, and in dashed lines old and new blades, and a section of tissue ribbon.

FIG. 2 is an exploded perspective view of the main parts of the blade holder used with the method of this invention.

FIG. 2A is an alternate cam shaft construction for the mentioned blade holder.

FIG. 3 is a plan view of the assembled blade holder of FIG. 2 and showing in dashed lines the position in which the disposable blade is placed in the holder.

FIG. 4 is a rear elevation of the holder of FIG. 3.

FIG. 5 is a right end elevation of FIG. 3 in unlocked position.

FIG. 6 is a left end elevation of FIG. 3 in unlocked position.

FIG. 7 is an elevation section view taken along line 7-7 of FIG. 3 in unlocked position.

FIG. 8 is an elevation section view taken along line 8-8 of FIG. 3 in unlocked position.

FIG. 9 is a view like FIG. 7 and showing a disposable blade in an unlocked position within the holder.

FIG. 10 is a view like FIG. 8 and showing the disposable blade in a locked position within the holder.

FIG. 11 is a plan view of a disposable blade used in the method of this invention.

FIG. 12 is an enlarged, fragmentary, elevation section view of the disposable blade.

FIG. 13 is an enlarged, fragmentary, section view of the disposable blade receiving portion of the unlocked holder of FIG. 8 but shown in a normal tilt, off vertical.

FIG. 14 is an enlarged fragmentary, section view of the disposable blade receiving portion of the locked holder of FIG. 10, but which is also shown in a normal tilt, off vertical.

FIG. 15 is a somewhat generalized view of a conventional disposable blade cartridge holder, as adapted to the invention.

DETAILED DESCRIPTION The method of the invention will be explained in conjunction with an explanation of an apparatus adapted to practice the method.

Referring to FIG. 1, a conventional, rotary microtome 10 comprises a housing 1 1 having the customary gearing for moving the specimen holder 12 in a vertical reciprocatory path and at the same time feeding or advancing holder 12 outwardly against a stationary knife. The knife clamp microtome 11 is generally indicated at 13 and is the conventional John Hopkins clamp for the American Optical Company, Spencer 820 microtome which is used in illustration. Knife clamp 13 is adjustable rotatably, laterally, and forwardly as indicated by the arrows in FIG. 1 and the knife is adjustable vertically in the clamp so that the knife can be adjusted for the proper clearance angle, tilt vertical and lateral position.

Adjusting screws 16 provide vertical blade adjustment, rotatable arm 17 locks clamp 13 in the selected forward position and arms 18 lock the clamp in the selected tilt position. While most microtome knife clamps provide precision lateral, tiltable, forward and vertical positioning of the knife or clamp in order to obtain precise knife positions some clamps do not necessarily have all of these adjustments or some or all of the adjustments are locked in a selected position and never disturbed. For example, if the type of tissue is uniform or the knife positioning is not critical, the-clamp can be used in some predetermined position. The foregoing is mentioned because the method of the invention adapts to either .type of microtome operation.

Knife clamp 13 has a pair of jaws 14, 15 against which the slotted end portions of the disposable blade holder of the invention are securely held in the clamp. That is, the space normally occupied by the conventional microtome knife is instead occupied by the blade 7 holder of the invention, the invention blade width W being at most a minor portion of the conventional knife width. 7

The blade holder in the preferred form for practicing the method of the invention is comprised of five parts, two of which are movable. Support for the disposable blade is provided by a backing plate 20 which resides in clamp 13 and has slotted end portions which extend outside the respective jaws 14, 15. Backing plate 20 has beginning at its uppermost edge 20a, a precision formed concave surface 21 which in use receives and provides a precise backing surface for curing the disposable blade and which extends downward a predetermined distance corresponding to the width W of disposable blade 50, and across the complete length L of plate 20. Here it should be noted that concave surface 21 may be precision formed in a central portion of a lesser lengthX corresponding to the length of mating pivotal clamping plate (later described) since the blade is bent by plate 65. However, the end portions of surface 21 if not precision formed should be formed so as not to interfere with the bending operation.

At the base of concave surface 21 is a shallow ledge 22 which acts as a stop or rest and supports the disposable blade 50 to be later described. 'A flat face 23 extends downward from ledge '22. Face 23 has threaded holes 24, 25, 26, 27, 28, 29, 30 and 31 which extend into plate 20 a predetermined distance. Near the bottom edge of plate 20 there is a semi-circular groove 32 which extends into and across plate 20. Immediately adjacent the bottom of plate 20 and extending upwardly to the bottom edge of groove 32 is a small flat face area 33. The back of plate 20 is precision formed flat which provides a precision flat back clamping surface for clamping the blade holder of the invention in the jaws 14, 15 of the conventional knife clamp 13.

Opening and closing of the blade holder, i.e., pivoting of plate 65, is controlled by a rotatable cam shaft member 60 whose ends terminate in a pair of stops 61, 62 formed integral therewith and which act to prevent axial movement of shaft 60 in groove 32 of backing plate 20. When the blade holder of the invention is assembled, stops 61, 62 reside on the ends of back plate 20 as best shown in FIGS. 3 and 4. Shaft 60 has an integral extension which extends outward and downward from stop 61 and provides a finger grip or manual control member 63 for the operator to use in rotating cam shaft 60. Shaft 60 also has a flat side 64 cut therein which provides a flat side whose function will be described later.

A pair of identical clamping plates 35, 36 are adapted to be fixedly mounted on plate 20. Since plates 35 and 36 are identical, only plate 35 will be described in detail and it will be seen that plates 20, 35 and 36 form an essentially integral structure. Clamping plate 35 has a flat inner face 37 which matches flat'face 23 of plate 20. Also, a semi-circular groove 38 mates'with groove 32 of plate and together form a circular opening 39. Upward a predetermined distance from groove 38 is an inward angled flat surface 40. Surface 40 extends upward a predetermined distance so that uppermost edge 41 is in alignment with edge 20a of backing plate 20. At this point, edge 40 extends outward forming a flat ledge 42. Ledge 42 when extends downward at a predetermined angle a predetermined distance to form a sloped, precision formed, clamping face 43 which joins a flat front face 44. Face 44 has three threaded holes therein 45, 46, 47 mating respectively with threaded holes 24, 25, 26 in plate 20. Holes 45, 46, 47 are recessed so that the screw heads of screws 48, 49, 54 will remain flush with face 44. Once screws 48, 49, 54 are tightened, clamping plate 35 is held firmly in place against backing plate 20. As previously stated, clamping plate 36 is identical to clamping plate 35 and is held firmly in place by screws 55, 52, 53 mating with holes 29, 30, 31 respectively. Clamping plates 35, 36 thus hold cam shaft 60 in place but with freedom to rotate. While shown as three separate parts plates 20, 35 and 36 could of course be made as an integral unit and cam shaft 60 mounted accordingly and made with one (FIG. 2) or two finger grips (FIG. 2A).

A central pivotal plate 65 fits within the lateral spacing of clamping plates 35 and 36 and as later explained provides means for clamping blade 50 and the front surface of plate 65 also serves as a guide for the cut tissue, whether in individual sections or in ribbon form. Plate 65 has a convex, precision formed, sloping surface 66 which mates with concave surface 21 of backing plate 20 and it is between these precision surfaces that blade 50 is bent and clamped. The base of convex surface 66 joins a flat surface 67 which extends downward from surface .66 and in use mates with the opposing portion of surface 23 of plate 20. A square shaped slot 68 is cut into surface 67 adjacent the bottom edge. Square slot 68 aligns with semi-circular grooves 32 and 38 to form an opening for the full length of the holder and in which resides shaft 60. Slot 68, unlike groves 32 and 38 has straight side walls with no curvature and is designed so that flat side 64 of shaft 60 when the holder is open as in FIG. 8 aligns with and rests against surface 68' (FIG. 8) of slot 68. A flat surface 69 on plate .65 mates with flat surface 33 of backing plate 20. A flat exterior surface 70 generally aligns with faces 44 of clamping plates 35, 36. A pair of unthreaded holes 71, 72 are formed in pivotal plate 65 which is pivotally secured to backing plate 20 by screws '73, 74 which pass through holes 71, 72 of somewhat larger diameter, and are screwed into holes 27, 28. A front tapered angle and precision formed and polished surface 75 extends from surface 70 to the end of convex slope 66 and it is this surface which receives and smoothly guides the cut tissue and enables the formation of ribbons of tissue for mass sectioning as required for film mounted tissue. Blade changes do not disturb ribbon R.

As previously stated, disposable blades 50 suitable for use with the method of this invention but without the usual guard member are manufactured and sold under various trademarks such as Personna and Week.

The desired character is illustrated by a description of blade 50. Blade is of a length L-l preferably greater than the length L-2 of pivotal plate 65 and is substantially greater in length than standard single or double edge razor blades so that cuts can be taken from larger specimen blocks. That is, a specimen block up to at least L-2 length can be cut. In one embodiment, blade 50 is a Week blade 2 by A inch approximately, and of 0.010 inch thickness which allows the blade to be slid into the blade holder from the side and so that it resides between concave slope 21 and convex slope 66 and rests on ledge 22 of backing plate 20. Blade 50 preferably has a compound angled edge of microtome knife edge cutting quality but unlike single edge razor blades now on the market, blade 50 has no guard or bending member on the non-cutting edge. That is, the

conventional Week or Personna single edge surgical blade is modified according to the method of the invention by having the guard member removed. Removal of the guard member substantially enhances blade flexibility. Stainless steel is a preferred material for use inmaking blade 50. Chrome-carbon blades are acceptable where shorter storage periods exist and corrosion is no problem. v

Reference will now be directed t the operation of the disposable blade and blade holder according to the method of this invention. Once the holder is assembled as described and illustrated in FIG. 2, microtome clamp 13 is adjusted or tilted into an approximate 15 position towards feeding holder 12. The disposable blade holder of the invention is slid into the clamp 13 endwise so that clamping plates 35, 36 are in central alignment with jaws 14, 15. Once in position, jaws 14, 15 are tightened on the precision sloped surfaces 43 of clamp plates 35, 36 and effectively lock the blade holder in clamp 13. Finger grip or control member 63 is turned so that flat side 64 of shaft is in alignment with surface 68' of slot 68 of pivotal plate 65. With shaft 60 in this unlocking position, blade 50 is slid into the holder from the side through the slotted end portions so that blade 50 rests on ledge 22 between concave sloping surface 21 and convex sloping surface 66. Note here that plates 35, 36 and 20 form fixed blade shaped slots S S (FIG. 5, 6) through which blade 50 can he slid from the side in a snug, slidable fit. Two slots 8,, S insure the ability to push out the old blade with the new blade. With only one slot S the old blade can be lifted vertically, however the presence of two slots 8,, S is much preferred. Also it is desirable that the slot be sufficiently narrow so as to prevent an incoming blade sliding past a worn blade that is intended to be removed. Once the blade 50 is in position, shaft 60 is rotated by turning finger grip 63 towards the operator. As shaft 60 is rotated, flat side 64 is rotated away from slot 68 and the circular portion of shaft 60 is brought into contact with surface 68' of slot 68 which causes central pivotal plate to be pivoted slightly. FIGS. 13 and 14 more clearly illustrate what takes place. FIG. 13 illustrates the open position or position in which shaft 60 has not yet been rotated but blade 50 has been placed in the holder in a snug fit. FIG. 14 shows plate 65 pivoted forward slightly about the edge of ledge 22 by the camming effect of shaft 60 with slot 68. Convex surface 66 is moved forward against substantially the whole plane of blade 50 so that blade 50 is bent uniformly around a longitudinal axis until it is against concave surface 21. At this point, shaft60 assumes a locked position holding blade 50 curved and with the edge of blade 50 stiffened and angled for proper cutting. This curving of blade 50 along with the tilting of clamp 13 provides a preferred total clearance angle of approximately 30 for plate 50s leading edge surface. Solid blade support is provided by ledge 22.

Blade 50 once dulled can be replaced by reversing finger grip 63 so as to turn cam member 60 back to the position of FIG. 8 which releases the blade. Blade 50 is then pushed endwise out of the holder as a new blade is being pushed in. Of significant importance is the fact that blades can be changed without removing the holder from clamp 13 or adjusting the blade holder position, which in turn eliminates loss of valuable sections due to retrimming of the section block as is necessary in disposable blade holders now in use. Furthermore, the critical ribbon guide surface 75 on plate 65 is not disturbed. Replacement blades are easily installed by simply turning cam shaft 60 into an unlocking position and inserting a new blade from either side usually determined by the operator being left or right handed. At not time is the operator exposed to sharp edges, which could nick or cut, while inserting a new blade. Blade thickness and curvature insure locking of shaft 60. That is, the thickness, curvature and position of the blade are selected to provide resilient forces which releasably lock member 60 in position.

The blades may, if desired, be stored in a cartridge of the ejector type. As generally shown in FIG. 15, the finger pusher 80 moves ejector bar 81 from the retracted dashed line position to the ejecting position shown in solid lines and pushes out a new blade 50. Such a cartridge holding 25 blades has been built of clear Lucite plastic and used by pushing out the old blade with a new blade being ejected from the cartridge and allowing bar 81 to enter the holder slot. The length of bar 81 and travel of pusher 80 are designed so that bar 81 may enter the holder slot and exactly position blade 50. Springs 82 gradually move the blades up one by one.

The method of the invention thus eliminates conventional knives which are expensive in initial cost and require expensive and time consuming resharpening operations and equipment as well as extra technician time for resharpening. Also, with conventional methods of using microtome knives repositioning of the knife clamp upon changing knives is necessary since each knife has a different dimension due to the wearing away of the material during sharpening. This has been eliminated. The method of the invention has furthermore overcome the problem of chattering or edge vibration experienced in prior art methods based on cutting with wafer type disposable blades. Of particular significance is that by modifying the Week or Personna type surgical blade by removing the guard member a disposable blade is obtained which when clamped and used according to the method of the invention provides cutting at least equal to and in many applications superior to methods based on microtome knife edge cutting quality. Removal of the guard member allows the blade to be flexed, i.e., curved around a longitudinal axis. Thus, even though the blade of the invention is normally difficult to flex, e.g., simply by holding and pressing between the fingers it is made to flex sufficiently for the method of the invention by applying the force of the concave surface 66 over substantially the whole blade surface and using precision pressing and backing surfaces (66, 21). The amount of curvature imposed on blade 50, preferably on about 1 inch radius, is variable by adjusting screws 73, 74. Unlike prior art disposable blades and holders, e.g., US. Pat. No. 1,865,539, blade 50 is not required to be tensioned longitudinally. Since the holder and blade used in the method of the invention can be and necessarily are precision made each new blade acts precisely 1 as the blade before and irrespective of the nature of the specimen. Once blade clamp 13 has its lateral, tilt, vertical and forward positions adjusted, the adjustments may be ,locked and never again disturbed. All that is required to get a fresh cutting edge and renew the cutting operation is to simply replace blade 50 by unlocking plate 65, installing new blade 50 and then locking plate 65. Such precision cutting therefore conforms to the precision of the microtome itself an accomplishment not heretofore achieved. Blade thickness, curvature and positioning always insure obtaining the same precise locked position of the parts.

To better visualize the implications of the method of the present invention the following steps are generally involved when using the conventional microtome knife method of cutting:

l. Clamp blade at both ends in holder 2. Adjust blade position roughly a. Laterally b. Forwardly c. In tilt d. Vertically 3. Take trial cuts to trim block and align face 4. Take trial sections 5. Readjust blade position finely as required a. Laterally b. Forwardly c. In tilt d. Vertically 6. Trim sections until blade edge is dulled 7. Either: Replace blade or shift blade laterally to get sharp edge 8. Cut trial sections to test new edge 9. Readjust blade position finely as required:

a. Laterally b. Forwardly c. In tilt d. Vertically 10. Trim sections until edge is dulled l 1. Repeat all of above steps for each new blade or new blade edge Since the conventional blade is non-disposable the following steps are also required each time the blade is resharpened:

12. Install blade in honing machine 13. Install glass honing plates 14. Rough ho'ne blades against glass plates 15. Strop or fine hone blades 16. Remove resharpened blades and store Furthermore, since blade resharpening requires that honing plates be periodically resurfaced; these rehoning steps are involved:

17. Install in hone plate resurfacing machine 18. Roughly hone plates on one side 19. Finely hone plates on same side 20. Invert plates and repeat rough and fine honing on opposite side 21. Remove and store plates 7 Without reciting the precise blade positioning and bending steps covered in the preceding description and in the language of the claims, it can generally be observed that the method of the invention involves only the following steps:

1. Clamp blade holder atboth ends in knife holder 2. Install disposable blade in blade holder 3. Adjust blade holder position roughly a. Laterally b. Forwardly c. In tilt d. Vertically 4. Take trial cuts to trim block and align face 5. Take trial sections 6. Readjust blade position finely as required a. Laterally b. Forwardly c. In tilt d. Vertically 7. Trim sections until edge is dulled 8. Replace blade only but do not repeat any of above steps since blade position is automatically restored From the above, the sharp contrast between the usual prior art method and the method of the invention is more precisely seen. It should of course be understood that the above is a very generalized comparison and assumes that in both cases the technician is concerned with serial sectioning of the same type block. Whenever the type block is changed both prior art and the present method of course require certain trial and error cuts to initiate proper sectioning. In any case, however, the present method very dramatically I and substantially reduces the number of steps involved ployed. Here only forward and backward adjustment of the clamp would be required. The method of the invention thus adapts to many and various kinds of holders, clamps and the like.

What is claimed is: l. The method of microtome cutting of an embedded specimen comprising the steps of:

a. mounting the specimen in a holder mechanism having means for reciprocating and advancing the specimen for precision cutting in a vertical plane;

b. mounting forward of the mechanism a blade holder having a backing member providing a fixed central, smooth precision formed concave backing ble clamping member having on one back side a convex clamping surface mating said concave backing surface and on the opposite front side a smooth concave guide surface adapted to receive and allow the undisturbed flow of cut ribbons of 1 tissue, and means to move said clamping member towards and away from said backing member, said mounting of said blade holder being effected in such manner that said concave backing surface assumes a predetermined optimum position relative to said cutting plane;

0. moving said clamping member away from said backing member sufficient to form'a slot between said concave backing and convex clamping surfaces and which with the slots provided by said holder end portions forms a continuous slot across said holder;

d. inserting from one side of said holder slot a substantially rectangular uniform size disposable I blade having one longitudinal edge precision sharpened to microtome knife quality for cutting and i the opposed edge free of the conventional guard member and being of substantially less flexibility than the conventional double edge wafer blade and positioning said blade with its central portion opposite said backing surface and its ends in said end portion slots;

e. moving said clamping member toward said backing member whereby the central portion of said blade is clamped between said concave backing and convex clamping surfaces, said blade is slightly curved around a longitudinal axis to bring its cutting edge into said cutting plane and at an appropriate optimum angle with respect thereto and said clamping member is locked in such clamped position; 7

f. cutting a predetermined number of sections from said specimen while allowing individual sections and ribbons of tissue to form and flow on said clamping member front guide surface and until said blade cutting edge is worn;

, g. without disturbing the position of said holder end portions moving only said clamping member away from said backing member whereby to release said worn blade and restore said slot across said holder;

h. removing said worn blade from one side of said holder and installing a new said uniform blade in the same position previously occupied by the worn blade;

i. moving said clamping member toward said backing member as before to place the cutting edge of the new said blade in said cutting plane and at the same said optimum angle; and

j. continuing to repeat the foregoing steps until the required number of tissue sections have been cut.

2. The method of claim 1 including the steps of:

a. after mounting and clamping said blade and prior to cutting usable sections cutting a series of test sections and during such test cutting adjusting said blade holder and blade as required laterally, in tilt,- forwardly and vertically to obtain respective optimum positions of said holder and blade; and

b. thereafter always maintaining said blade holder in its said optimum position during blade changes and after each respective blade change restoring each successive blade to the same said optimum blade position.

. The method of claim 1 including the steps of:

mounting said blade holder in a conventional microtome non-disposable knife holder having a pair of clamps adapted to clamp said end portions and having adjustment means to adjust said blade holder in tilt, laterally, vertically and forwardly;

. utilizing said adjustment means to bring said blade holder and blade into optimum positions with respect to said cutting plane; and

. thereafter during replacement of each successive new said blade maintaining said blade holder in said optimum holder position and adjusting only said clamping member to bring the new replaced blade into the same said optimum blade position.

4. The method of claim 1, including the step of removing each successive worn blade by pushing from the side and on one end of the worn blade with one end of the next successive new blade until the worn blade is ejected from said holder slots and the new blade has assumed the position previously occupied by the worn blade.

5. The method of claim 1 including the steps of:

a. storing replacement blades in a cartridge type dispenser; and

b. pushing each respective worn blade out of said holder with a new blade being ejected from said cartridge.

6. The method of claim 1 including the step of installing the blade such that both of its ends extend at least slightly beyond the width of the specimen being cut.

7. The method of claim 1 including the step of adjusting the amount of pressure applied by said clamping member to said blade to regulate the curvature thereof.

8. The method of claim 1 wherein said concave backing surface merges at its bottom end with a ledge formed in said backing member and including the step of supporting each said blade on said ledge during cutting.

9. The method of claim 1, wherein the consecutive steps of moving said clamping member away from said backing member, removing said worn blade from one side of said holder and installing a new said blade, and moving said clamping member toward said backing member are performed within such limits of movement that any ribbon of sections previously cut and supported on said clamping member front guide surface remains unbroken and otherwise undisturbed. 

1. The method of microtome cutting of an embedded specimen comprising the steps of: a. mounting the specimen in a holder mechanism having means for reciprocating and advancing the specimen for precision cutting in a vertical plane; b. mounting forward of the mechanism a blade holder having a backing member providing a fixed central, smooth precision formed concave backing surface, a pair of fixed slotted integral end portions on opposite sides of said backing surface, a movable clamping member having on one back side a convex clamping surface mating said concave backing surface and on the opposite front side a smooth concave guide surface adapted to receive and allow the undisturbed flow of cut ribbons of tissue, and means to move said clamping member towards and away from said backing member, said mounting of said blade holder being effected in such manner that said concave backing surface assumes a predetermined optimum position relative to said cutting plane; c. moving said clamping member away from said backing member sufficient to form a slot between said concave backing and convex clamping surfaces and which with the slots provided by said holder end portions forms a continuous slot across said holder; d. inserting from one side of said holder slot a substantially rectangular uniform size disposable blade having one longitudinal edge precision sharpened to microtome knife quality for cutting and the opposed edge free of the conventional guard member and being of substantially less flexibility than the conventional double edge wafer blade and positioning said blade with its central portion opposite said backing surface and its ends in said end portion slots; e. moving said clamping member toward said backing member whereby the central portion of said blade is clamped between said concave backing and convex clamping surfaces, said blade is slightly curved around a longitudinal axis to bring its cutting edge into said cutting plane and at an appropriate optimum angle with respect thereto and said clamping member is locked in such clamped position; f. cutting a predetermined number of sections from said specimen while allowing individual sections and ribbons of tissue to form and flow on said clamping member front guide surface and until said blade cutting edge is worn; g. without disturbing the position of said holder end portions moving only said clamping member away from said backing member whereby to release said worn blade and restore said slot across said holder; h. removing said worn blade from one side of said holder and installing a new said uniform blade in the same position previously occupied by the worn blade; i. moving said clamping member toward said backing member as before to place the cutting edge of the new said blade in said cutting plane and at the same said optimum angle; and j. continuing to repeat the foregoing steps until the required number of tissue sections have been cut.
 2. The method of claim 1 including the steps of: a. after mounting and clamping said blade and prior to cutting usable sections cutting a series of test sections and during such test cutting adjusting said blade holder and blade as required laterally, in tilt, forwardly and vertically to obtain respective optimum positions of said holder and blade; and b. thereafter always maintaining said blade holder in its said optimum position during blade changes and after each respective blade change restoring each successive blade to the same said optimum blade position.
 3. The method of claim 1 including the steps of: a. mounting said blade holder in a conventional microtome non-disposable knife holder having a pair of clamps adapted to clamp said end portions and having adjustment means to adjust said blade holder in tilt, laterally, vertically and forwardly; b. utilizing said adjustment means to bring said blade holder and blade into optimum positions with respect to said cutting plane; and c. thereafter during replacement of each successive new said blade maintaining said blade holder in said optimum holder position and adjusting only said clamping member to bring the new replaced blade into the same said optimum blade position.
 4. The method of claim 1, including the step of removing each successive worn blade by pushing from the side and on one end of the worn blade with one end of the next successive new blade until the worn blade is ejected from said holder slots and the new blade has assumed the position previously occupied by the worn blade.
 5. The method of claim 1 including the steps of: a. storing replacement blades in a cartridge type dispenser; and b. pushing each respective worn blade out of said holder with a new blade being ejected from said cartridge.
 6. The method of claim 1 including the step of installing the blade such that both of its ends extend at least slightly beyond the width of the specimen being cut.
 7. The method of claim 1 including the step of adjusting the amount of pressure applied by said clamping member to said blade to regulate the curvature thereof.
 8. The method of claim 1 wherein said concave backing surface merges at its bottom end with a ledge formed in said backing member and including the step of supporting each said blade on said ledge during cutting.
 9. The method of claim 1, wherein the consecutive steps of moving said clamping member away from said backing member, removing said worn blade from one side of said holder and installing a new said blade, and moving said clamping member toward said backing member are performed within such limits of movement that any ribbon of sections previously cut and supported on said clamping member front guide surface remains unbroken and otherwise undisturbed. 